The first year after childbirth is highly stressful for many mothers, but enhanced activity of the "bonding hormone" oxytocin (OT) may decrease blood pressure (BP), sympathetic and corticosterone activity, and stress behavior, while increasing positive affect and activation of central reward pathways during mother- infant contact. Currently in the US, roughly 60% of new mothers return to work within the first year, increasing the mother's total workload while markedly decreasing the time available for mother-infant contact in the child's early life. In 3 translational studies, we found that mothers who decreased their OT levels during a lab stressor that followed warm contact with their infants had higher BP levels before, during and after stress than mothers who increased OT;OT decrease mothers were more likely to be bottle- than breast- feeders. Higher OT response of mothers with young infants (<5 months) was also related to lower ambulatory BP at home. Preliminary data suggests that lower OT response in African American mothers with infants less than 5 months old may be linked to early return to work outside the home. We hypothesize that during the first year postpartum, decreased maternal OT activity is related to less frequent mother-infant interactions and less warm physical contact between them (including breast-feeding), and that increasing such contacts are beneficial for both mother and infant. Thus, we will recruit 120 mother-infant dyads (including 48 African American) to address the following questions: 1. At 2-3 months postpartum, is OT response after warm infant contact lower in mothers who have vs. have not returned to work, and who have vs. have not weaned their infants from breast feeding? 2. Is prior physical touch with their infant essential to elicit maternal OT increases, or is face-to-face interaction without touch equally effective? 3. Using a prospective, within-dyad study with testing at 2-3 months and again at 1 year, is higher maternal OT response at initial testing associated with lower ambulatory BP at home, and with higher maternal attachment scores and higher quality mother-infant interaction, and does it predict higher quality interaction at age 1 year? All 120 mothers will undergo 2 days of 24-hour BP monitoring, so that working mothers are monitored on a day spent with vs. a day spent apart from their babies. Maternal OT response will also be related to 24-hour urinary catecholamine and cortisol on both days. Also, in a pilot feasibility component, mother and infant salivary and urinary measures of OT will be obtained concurrently with maternal blood- derived OT, to provide initial tests of the capability to assess OT activity with non-invasively obtained samples. This research will provide insights into the effect of the frequency and type of early mother-infant interactions on neurobehavioral pathways influencing their physiological, behavioral and affective responses, which may have profound implications for the health and well-being of both mother and child.